1. Field of the Invention
The present invention relates to an image forming apparatus used with a replaceable process cartridge mounted therein.
2. Description of the Related Art
Conventionally, in an image forming apparatus used with a process cartridge mounted therein, when the residual amount of toner filled in the process cartridge decreases, a notification is sent to a user to replace the process cartridge with a new process cartridge.
At this time, in order to correctly detect that the residual amount of toner decreases, for instance, the amount of consumed toner is accumulated whenever images are formed, then the toner consumption amount is compared with the capacity of the toner (reference value for determining ‘toner empty’) which has been stored in an image forming apparatus in advance, and then the residual amount is considered as decreased (toner empty state) when the consumption amount approaches the amount of the toner stored in the image forming apparatus (refer to JP-A-2001-80163 (for instance, after section [0020]).